1. Technical Field of the Invention
The present invention relates to a vehicle power generation controlling device and a vehicle system, in which the vehicle generation controlling device controls a power generation state of a vehicle power generator mounted on a passenger car, a truck, and the like.
2. Description of the Related Art
A vehicle power generation controlling device detects a voltage at a control terminal (a plus terminal of a battery or an output terminal) and compares the detected voltage with a reference value. When the voltage at the control terminal is higher than the reference value, the vehicle power generation controlling device turns OFF a transistor that controls ON/OFF of a field current. On the other hand, when the voltage is lower than the reference value, the vehicle power generation controlling device turns ON the transistor. As a result, the vehicle power generation controlling device controls a duty factor of a field winding and controls the voltage at the control terminal to maintain the voltage at a constant value.
When an electrical load is applied, electric current of an amount corresponding to the applied electrical load is taken from a battery. An amount by which the voltage drops as a result of the electric current being taken is controlled such that the voltage at the control terminal is a regulated voltage, by the duty factor of the field winding being increased and an amount of generated power being increased. The control is performed instantly. Therefore, voltage drop at the control terminal is minimal, and the voltage is maintained at an almost constant value. However, at this time, a power generation torque of the vehicle power generator suddenly increases because of the sudden increase in the field current of the vehicle power generator. As a result, engine speed decreases. In an idle rotation range in particular, the engine may stall as a result of the decrease in the engine speed.
As a conventional technology for preventing a phenomenon such as this from occurring, for example, a following method is disclosed in Japanese Patent Application Laid-Open Publication No. 5-300669. In the method, speed at which the duty factor of the field winding increases is restricted when the field current increases, thereby suppressing a sudden increase in the power generation torque of the vehicle power generator. This method is a function for suppressing power generation by the vehicle power generator. Therefore, although torque variations can be suppressed, the amount of generated power becomes insufficient while this function is running and output voltage from the vehicle power generator drops.
In the conventional method disclosed in Japanese Patent Application Laid-Open Publication No. 5-300669, the output voltage drops as a result of the restriction to the speed at which the duty factor of the field winding is increased when the electrical load is applied. As a result, a problem occurs in that, when headlamps are illuminated, the headlamps may flicker.
When deceleration occurs while the output current is in a constant state, the vehicle power generator performs control to increase the field current to maintain the output current. Whether the above-described function for suppressing the speed at which the field current increases runs during deceleration is decided based on whether an amount of increase in the field current required as a result of deceleration is greater than a limit value of the speed at which the field current increases. In other words, when a degree of deceleration of a vehicle is large (when a deceleration rate during deceleration is large), the amount of increase in the field current required as a result of deceleration becomes large. A possibility that the amount of increase in the field current is greater than the limit value of the speed at which the field current can increase becomes high. Therefore, the probability of the above-described function for suppressing the rate of increase of the field current being activated becomes high.
Therefore, when a vehicle on which the vehicle power generator having the function for suppressing the speed at which the field current increases is mounted decelerates, the function for suppressing the speed at which the field current increases may run even when the electrical load is constant. Variations in engine speed are suppressed as a result of the function running. However, the output voltage drops. Therefore, when the vehicle decelerates while the headlamps are turned on, the headlamps flicker because of the drop in output voltage.